A036-0020
Modeling Study of the Impact of COVID-19 on Air Quality in Southern California

Tuesday, 8 December 2020
Poster
Zhe Jiang, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, Hongrong Shi, Institute of Atmospheric Physics, Beijing, China, Bin Zhao, Pacific Northwest National Laboratory, Richland, WA, United States, Yu Gu, UCLA 405 Hilgard Ave, Los Angeles, CA, United States and Kuo-Nan Liou, University of California Los Angeles, Joint Institute for Regional Earth System Science and Engineering, Los Angeles, CA, United States
Abstract:
In response to the emergence of coronavirus (COVID-19), statewide stay-at-home orders took effect on March 19, 2020 in California. This brought abrupt and dramatic reductions in the vehicle traffic and industrial activities which are the major sources of southern California’s air pollution. The COVID-19 crisis offers us an unprecedented chance to evaluate the effectiveness of emission reductions on air quality. The Weather Research and Forecasting model with Chemistry (WRF-Chem) in combination with surface observations was applied during February 18 to April 23, 2020 to study the impact of COVID-19 on air quality in southern California. Based on the statistics of energy consumption and traffic flow changes, we adjusted the emission inventory considering the emission reduction during COVID-19 lockdown. The adjusted emission inventory is shown to be consistent with the emission inventory based on the satellite observations. The simulated magnitude and temporal evolution of key air pollutants (concentrations of fine-particulate matter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2) and 8h-maximum ozone (O3_8hmax)) using the adjusted emission inventory agree reasonably better with surface observations than simulation results without considering the COVID-19 induced emission reductions. We investigated the effects of reduced emissions and meteorology on air pollution, respectively. The levels of NO2 and PM2.5 decreased by up to 26.4% and 12.8% in southern California in the five weeks after the stay-at-home orders due to reduced emissions. For O3_8hmax, the emission reduction caused a decrease in rural areas but a slight increase in the urban areas. In order to further investigate the effects of emission reductions on ozone concentration, we conduct sensitivity experiments by changing reactive organic gases (ROG) and NOx controls. This study provides important insight into the development and optimization of effective air pollution control strategies in southern California.
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